The present invention is a method and apparatus to remove the adverse effects due to the imbalance between in-phase (I) and quadrature (Q) channels for I-Q demodulators and modulators in multi-carrier systems. A first balancer generates a first balancing signal from a first signal of a first index corresponding to a first frequency. A first combiner combines the first balancing signal and a second signal of a second index corresponding to a second frequency. The second frequency is symmetrical to the first frequency with respect to a center frequency in a multi-carrier composite signal. The first combiner generates a first balanced signal corresponding to the second frequency.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An apparatus comprising: a first balancer to generate a first balancing signal from a first balancing parameter and a first signal of a first index corresponding to a first frequency, the first balancing parameter being calculated in a training process and the first signal being provided by a first sub-carrier demodulator operating at the first frequency; and a first combiner coupled to the first balancer to combine the first balancing signal and a second signal of a second index corresponding to a second frequency, the second frequency being symmetrical to the first frequency with respect to a center frequency in a multi-carrier signal, the first combiner generating a first balanced signal corresponding to the second frequency.
2. The apparatus of claim 1 wherein the first balancer comprises: a first converter to convert the first signal into a first complex conjugate; and a first multiplier coupled to the first converter to multiply the first complex conjugate with the first balancing parameter, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal.
3. The apparatus of claim 1 wherein the first combiner includes a first subtractor to subtract the first balancing signal from the second signal to provide the first balanced signal.
4. The apparatus of claim 1 wherein the first balanced signal is the same as a first desired signal free of imbalance effects, excluding scaling by a first deterministic complex factor.
5. The apparatus of claim 4 wherein the first desired signal is an ideally demodulated signal free of imbalance effects.
6. The apparatus of claim 1 further comprising: a second balancer to generate a second balancing signal from a second balancing parameter and the second signal, the second balancing parameter being calculated in a training process; and a second combiner coupled to the second balancer to combine the second balancing signal with the first signal at a second frequency, the second combiner generating a second balanced signal at the first frequency.
7. The apparatus of claim 6 wherein the second balancer comprises: a second converter to convert the second signal into a second complex conjugate; and a second multiplier coupled to the second converter to multiply the second complex conjugate with the second balancing parameter, the second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
8. The apparatus of claim 6 wherein the second combiner includes a second subtractor to subtract the second balancing signal from the first signal to provide the second balanced signal.
9. The apparatus of claim 6 wherein the second balanced signal is the same as a second desired signal free of imbalance effects, excluding scaling by a second deterministic complex factor.
10. The apparatus of claim 9 wherein the second desired signal is ideally demodulated signal free of imbalance effects.
11. The apparatus of claim 6 wherein the second signal is provided by a second sub-carrier demodulator operating at the second frequency.
12. The apparatus of claim 6 wherein the second balancing parameter is a ratio between an output of a first sub-carrier demodulator and a conjugate output of a second sub-carrier demodulator when the multi-carrier signal contains a first sub-carrier signal modulated by a null complex number and a second sub-carrier signal modulated by a non-null complex number during the training process.
13. The apparatus of claim 6 wherein the first balanced signal is provided to a second sub-carrier modulator operating at the second frequency and the second balanced signal is provided to a first sub-carrier modulator operating at the first frequency.
14. The apparatus of claim 13 wherein: the first combiner includes a first subtractor coupled to the first balancer to subtract the first balancing signal from the second signal at a first frequency, the first subtractor generating the first balanced signal at the second frequency; and the second combiner including a second subtractor coupled to the second balancer to subtract the second balancing signal from the first signal at a second frequency, the second subtractor generating the second balanced signal at the first frequency.
15. The apparatus of claim 14 further wherein: the first balancer comprises: a first converter to convert the first signal into a first complex conjugate; and a first multiplier coupled to the first converter to multiply the first complex conjugate with the first balancing parameter, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal; and the second balancer comprises: a second converter to convert the second signal into a second complex conjugate; and a second multiplier coupled to the second converter to multiply the second complex conjugate with a second balancing parameter, the second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
16. The apparatus of claim 15 wherein the first balanced signal and the second balanced signal are a first pre-distorted signal and a second pre-distorted signal, respectively.
17. The apparatus of claim 16 wherein the first pre-distorted signal and the second pre-distorted signal are provided to a second sub-carrier modulator operating at the second frequency and a first sub-carrier modulator operating at the first frequency, respectively.
18. The apparatus of claim 17 wherein the first balancing parameter is derived from outputs of first and second ideal sub-carrier demodulators operating at first and second frequencies when the multi-carrier signal is generated from the first and second sub-carrier modulators modulated by the first and second desired signal, the first desired signal being a non-null complex number and the second desired signal being a null complex number during the training process.
19. The apparatus of claim 17 wherein the second balancing parameter is derived from outputs of first and second ideal sub-carrier demodulators operating at first and second frequencies when the multi-carrier signal is generated from the first and second sub-carrier modulators modulated by the first and second desired signal, the first desired signal being a null complex number and the second desired signal being a non-null complex number during the training process.
20. The apparatus of claim 1 wherein the first balancing parameter is a ratio between an output of a second sub-carrier demodulator and a conjugate output of a first sub-carrier demodulator when the multi-carrier signal contains a first sub-carrier signal modulated by a non-null complex number and a second sub-carrier signal modulated by a null complex number during the training process.
21. The apparatus of claim 1 wherein the first signal and the second signal are a first desired signal and a second desired signal to be transmitted, respectively.
22. The apparatus of claim 1 wherein at least one of the first and second indices corresponds to a zero index.
23. The apparatus of claim 22 wherein at least one of the first and second signals corresponds to one of the center frequency and a DC of a baseband signal of the multi-carrier signal.
24. A method comprising: calculating a first balancing parameter in a training process; generating a first balancing signal from a first balancing parameter and a first signal of a first index corresponding to a first frequency using a first balancer, the first signal being provided by a first sub-carrier demodulator operating at the first frequency; and combining the first balancing signal and a second signal of a second index corresponding to a second frequency using a first combiner, the second signal being provided by a second sub-carrier demodulator operating at the second frequency and the second frequency being symmetrical to the first frequency with respect to a center frequency in a multi-carrier signal, the first combiner generating a first balanced signal corresponding to the second frequency.
25. The method of claim 24 wherein generating a first balancing signal comprises: converting the first signal into a first complex conjugate by a first converter; and multiplying the first complex conjugate with the first balancing parameter by a first multiplier, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal.
26. The method of claim 24 wherein the first combiner includes a first subtractor to subtract the first balancing signal from the second signal to provide the first balanced signal.
27. The method of claim 24 wherein the first balanced signal is the same as a first desired signal free of imbalance effects, excluding scaling by a first deterministic complex factor.
28. The method of claim 27 wherein the first desired signal is a first ideally demodulated signal free of imbalance effects.
29. The method of claim 28 further comprising: calculating a second balancing parameter in a training process; generating a second balancing signal from a second balancing parameter and the second signal using a second balancer; and combining the second balancing signal with the first signal at a second frequency using a second combiner, the second combiner generating a second balanced signal at the first frequency.
30. The method of claim 29 wherein generating the second balancing signal comprises: converting the second signal into a second complex conjugate by a second converter; and multiplying the second complex conjugate with the second balancing parameter by a second multiplier, the second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
31. The method of claim 29 wherein the second combiner includes a second subtractor to subtract the second balancing signal from the first signal to provide the second balanced signal.
32. The method of claim 29 wherein the second balanced signal is the same as a second desired signal free of imbalance effects, excluding scaling by a second deterministic complex factor.
33. The method of claim 32 wherein the second desired signal is a second ideally demodulated signal free of imbalance effects.
34. The method of claim 29 wherein calculating the second balancing parameter results in a complex number derived from outputs of the first and second sub-carrier demodulators when the received multi-carrier signal contains a first sub-carrier signal modulated by a null complex number and a second sub-carrier signal modulated by a non-null complex number during the training process.
35. The method of claim 24 wherein calculating the first balancing parameter results in a complex number derived from outputs of the first and second sub-carrier demodulators when the received multi-carrier signal contains a first sub-carrier signal modulated by a non-null complex number and a second sub-carrier signal modulated by a null complex number during the training process.
36. A method comprising: calculating a first balancing parameter in a training process; generating a first balancing signal from a first balancing parameter and a first signal of a first index corresponding to a first frequency using a first balancer, the first signal being a first desired signal to be transmitted; and combining the first balancing signal and a second signal of a second index corresponding to a second frequency using a first combiner, the second frequency being symmetrical to the first frequency with respect to a center frequency in a multi-carrier signal, the first combiner generating a first balanced signal corresponding to the second frequency.
37. The method of claim 36 wherein the first balanced signal is provided to a sub-carrier modulator operating at the second frequency.
38. The method of claim 36 further comprising: generating a second balancing signal from the second signal by a second balancer; and combining the second balancing signal and the first signal at a second frequency by a second combiner, the second combiner generating a second balanced signal at the first frequency.
39. The method of claim 38 wherein generating the first and second balancing signals comprises: converting the first signal into a first complex conjugate by a first converter; multiplying the first complex conjugate with a first balancing parameter by a first multiplier, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal; converting the second signal into a second complex conjugate by a second converter; and multiplying the second complex conjugate with a second balancing parameter by a second multiplier, a second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
40. The method of claim 39 wherein the second signal is a second desired signal to be transmitted.
41. The method of claim 40 wherein the first balancing parameter is derived from outputs of first and second ideal sub-carrier demodulators operating at first and second frequencies when the multi-carrier signal is generated from a sub-carrier modulator operating at the first frequency and a sub-carrier modulator operating at the second frequency being modulated by the first and second desired signals, respectively, the first desired signal being a non-null complex number and the second desired signal being a null complex number during the training process.
42. The method of claim 40 wherein the second balancing parameter is derived from outputs of first and second ideal sub-carrier demodulators operating at first and second frequencies when the multi-carrier signal is generated from sub-carrier modulator operating at the first frequency and a sub-carrier modulator operating at the second frequency being modulated by the first and second desired signals respectively, the first desired signal being a null complex number and the second desired signal being a non-null complex number during the training process.
43. The method of claim 38 wherein the second balanced signal is provided to a sub-carrier modulator operating at the first frequency.
44. A system comprising: in-phase (I) and quadrature (Q) processing chains to generate I and Q samples from a multi-carrier signal having 2P sub-carrier signals at 2P carrier frequencies; a bank of demodulators coupled to the I and Q processing chains to demodulate the 2P sub-carrier signals, the bank of demodulators generating 2P demodulated signals; and a balancing unit coupled to the bank of demodulators to restore 2P original signals from the 2P demodulated signals, the balancing unit including P basic blocks, each of the basic blocks being coupled to a pair of the demodulators called the first and second sub-carrier demodulators of the basic block and comprising: a first balancer to generate a first balancing signal from a first signal at a first frequency, and a first combiner coupled to the first balancer to combine the first balancing signal and a second signal at a second frequency, the second frequency being symmetrical to the first frequency with respect to a center frequency in the multi-carrier signal, the first combiner generating a first balanced signal at the second frequency.
45. The system of claim 44 wherein the first balancer comprises: a first converter to convert the first signal into a first complex conjugate; and a first multiplier coupled to the first converter to multiply the first complex conjugate with a first balancing parameter, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal.
46. The system of claim 45 wherein the first balancing parameter is derived from outputs of the first and second sub-carrier demodulators when the multi-carrier signal contains a first sub-carrier signal modulated by a non-null complex number and a second sub-carrier signal modulated by a null complex number during a training process.
47. The system of claim 44 wherein the first combiner includes a first subtractor to subtract the first balancing signal from the second signal to provide the first balanced signal.
48. The system of claim 44 wherein the first balanced signal is a first desired signal scaled by a first complex factor.
49. The system of claim 48 wherein the first signal is provided by a first sub-carrier demodulator operating at the first frequency.
50. The system of claim 49 wherein the first desired signal is a first original signal.
51. The system of claim 50 wherein each of the basic blocks further comprising: a second balancer to generate a second balancing signal from the second signal; and a second combiner coupled to the second balancer to combine the second balancing signal with the first signal at a second frequency, the second combiner generating a second balanced signal at the first frequency.
52. The system of claim 51 wherein the second balancer comprises: a second converter to convert the second signal into a second complex conjugate; and a second multiplier coupled to the second converter to multiply the second complex conjugate with a second balancing parameter, the second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
53. The system of claim 52 wherein the second balancing parameter is derived from outputs of the first and second sub-carrier demodulators when the multi-carrier signal contains a first sub-carrier signal modulated by a null complex number and a second sub-carrier signal modulated by a non-null complex number during a training process.
54. The system of claim 51 wherein the second combiner includes a second subtractor to subtract the second balancing signal from the first signal to provide the second balanced signal.
55. The system of claim 51 wherein the second balanced signal is a second desired signal scaled by a second complex factor.
56. The system of claim 55 wherein the second signal is provided by a second sub-carrier demodulator operating at the second frequency.
57. The system of claim 56 wherein the second desired signal is a second original signal.
58. A system comprising: in-phase (I) and quadrature (Q) processing chains using I and Q samples to generate a multi-carrier signal having 2P sub-carrier signals at 2P carrier frequencies; a bank of 2P modulators generating 2P modulated signals of the 2P sub-carriers and the resulting I and Q samples to feed the I and Q processing chains; and a balancing unit generating 2P pre-distorted signals from 2P desired signals and using the 2P pre-distorted signals to modulate the 2P sub-carriers of the bank of 2P modulators, the balancing unit including P basic blocks, each of the basic blocks being coupled to a pair of the modulators called the first and second sub-carrier modulators of the basic block and comprising: a first balancer to generate a first balancing signal from a first signal at a first frequency, and a first combiner coupled to the first balancer to combine the first balancing signal and a second signal at a second frequency, the second frequency being symmetrical to the first frequency with respect to a center frequency in the multi-carrier signal, the first combiner generating a first balanced signal at the second frequency.
59. The system of claim 58 wherein the first signal is a first desired signal to be transmitted and the first balanced signal is the first pre-distorted signal provided to the second sub-carrier modulator operating at the second frequency.
60. The system of claim 59 wherein the second signal is a second desired signal to be transmitted.
61. The system of claim 58 further comprising: a second balancer to generate a second balancing signal from the second signal; and a second combiner coupled to the second balancer to subtract the second balancing signal from the first signal at a second frequency, the second combiner generating the second balanced signal at the first frequency.
62. The system of claim 61 wherein the second balanced signal is the second pre-distorted signal provided to the first sub-carrier modulator operating at the first frequency.
63. The system of claim 58 further comprising: a first converter to convert the first signal into a first complex conjugate; a first multiplier coupled to the first converter to multiply the first complex conjugate with a first balancing parameter, the first balancing parameter corresponding to the first frequency, the first multiplier generating the first balancing signal; a second converter to convert the second signal into a second complex conjugate; and a second multiplier coupled to the second converter to multiply the second complex conjugate with a second balancing parameter, the second balancing parameter corresponding to the second frequency, the second multiplier generating the second balancing signal.
64. The system of claim 63 wherein the first and second balancing parameters are obtained during a training process.
65. The system of claim 64 wherein the first balancing parameter is derived from outputs of first and second sub-carrier ideal demodulators operating at first and second frequencies when the multi-carrier signal is generated from the first and second sub-carrier modulators modulated by the first and second desired modulating signals, the first desired signal being a non-null complex number and the second desired signal being a null complex number during the training process.
66. The system of claim 64 wherein the second balancing parameter is derived from outputs of first and second sub-carrier ideal demodulators operating at first and second frequencies when the multi-carrier signal is generated from the first and second sub-carrier modulators modulated by the first and second desired modulating signals, the first desired signal being a null complex number and the second desired signal being a non-null complex number during the training process.
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August 2, 2001
February 13, 2007
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